1. Technical Field
The present disclosure relates to an image capturing system. More particularly, the present disclosure relates to a compact image capturing system applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand for a miniaturized optical system has been increasing. The sensor of a conventional photographing camera is typically a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor Sensor). As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for optical systems featuring better image quality.
A conventional optical system applied in a portable electronic product typically adopts a three-element lens structure, such as the one disclosed in the U.S. Pat. No. 8,081,393. Due to the popularity of mobile products with high-end specifications, such as smart phones and PDAs (Personal Digital Assistants), the requirements for high resolution and image quality of modern compact optical systems has been increasing significantly. However, the conventional three-element lens structure cannot satisfy these requirements of the compact optical system.
Thus, other conventional optical systems with four-element lens structure are disclosed such as the one disclosed in the U.S. Pat. No. 8,089,704. Since the axial distances between each two of the lens elements in the U.S. Pat. No. 8,089,704 are large and the arrangement of the axial distances is not appropriate. Therefore, it is not favorable for keeping this optical system compact. Moreover, the excessively curved surface change is not favorable for moldability.